The 2-(2-hydroxyphenyl)-2H-benzotriazoles represent a very important class of commercial UV-absorbers which have found wide-spread acceptance as stabilizers for protecting a host of organic substrates against the deleterious effects of exposure to actinic radiation.
With such a long period of commercial and technical interest in this class of compounds, there are a host of publications and patents describing this general class of compounds. Only a few of these references recite substitution of 2H-benzotriazoles with any group containing sulfur.
U.S. Pat. No. 3,218,332 disclose 2H-benzotriazoles substituted on the 5-position of the benzo ring by lower alkyl sulfone (i.e. lower alkylsulfonyl moieties). This reference also describes benzotriazoles substituted at the same position by sulfonamide, lower alkyl sulfonamides, or aryl sulfonate esters. Such sulfonamide substitution is also taught in U.S. Pat. Nos. 3,766,205 and 3,862,087.
The instant compounds and compositions are distinguished from the compounds of the prior art. None of these references disclose that substitution of a 2H-benzotriazole compound in the 5-position of the benzo ring by a sulfoxide or higher alkyl sulfone moiety results in a significant increase in UV absorbance and also shifts the absorption maximum by about 20 nm toward longer wavelength relative to benzotriazoles without such 5-thio substitution. Such increased absorbance coupled with the red shift of the absorbance maximum toward higher wavelengths enhances the protection of substrates sensitive to longer wavelength ultraviolet light (near visible), such as coatings, plastics and fibers.